The NSA has (at least) two separate missions: keep domestic systems secure, and break into foreign systems.

These systems come into conflict a lot because it has become nearly impossible to secure domestic systems without also securing foreign systems.

For a while, NSA appeared to favor securing domestic systems when the two came into conflict. Thus events like the withdrawal of SHA-0 and its strengthening and re-release as SHA-1.

Now, it appears to have swung back in the other direction, and pretty hard. They're keeping vulnerabilities secret and even deliberately introducing weaknesses in order to make their spying mission easier.

Educating the public about computer security aligns with one of their missions, and not the one they appear to really care about now.